Arizona ADU Laws

Phoenix's updated building construction code aligns with the city's broader commitment to sustainable growth in a desert environment. For backyard casitas and detached guest houses, this means new expectations around plumbing fixtures, water efficiency, and how interior square footage is planned and utilized. Key among these updates is alignment with EPA WaterSense standards for plumbing fixtures.

The City of Phoenix adopted the Phoenix Building Construction Code which includes an electric vehicle readiness requirement, the addition of EV charging infrastructure, on new builds in Phoenix to make it easier and more affordable to charge electric vehicles at home. In practical terms, this means new construction could include the conduit pathways and electrical panel capacity to support a future EV charging station — even if no charger is installed on day one.

Arizona's ADU laws represent a genuine expansion of your property rights—but they have a boundary at the HOA fence line. Understanding that distinction isn't a reason to abandon your casita plans, it just means you need the right team in your corner.

For years, building a backyard casita, guest house, or accessory dwelling unit in Arizona was an exercise in navigating a fragmented patchwork of local zoning codes. Whether you could build one and how large it could be depended almost entirely on which city or municipality your property sat within. That reality changed dramatically when Arizona passed a series of landmark bills collectively known as the "Casita Bills," most notably HB 2720 and its successor legislation HB 29